Temperature measuring method and apparatus, measuring mehtod for the thickness of the formed film, measuring apparatus for the thickness of the formed film thermometer for wafers

ABSTRACT

A temperature measuring apparatus, comprises a light splitting section for splitting the light radiated from a substrate into plural light components having wavelengths over a predetermined wavelength region, a detection section for detecting the intensities of the light components obtained by the light splitting section, an integrated value calculating section for calculating an integrated value of radiation intensity by cumulatively adding the intensities of the light components detected by the detecting section, and a surface temperature calculating section for calculating the surface temperature of the substrate from the integrated value, on the basis of reference data representing the relation between the temperature and the integrated value.

BACKGROUND OF THE INVENTION

[0001] When the film is formed on the semiconductor wafer in CVD thetemperature of a semiconductor wafer is measured by a radiationthermometer chamber, generally.

[0002] The radiation thermometer measures the wafer's temperature with aconstant emissivity.

[0003] However, if the emissivity of the object is unknown orchangeable, it is impossible to measure the temperature of the objectaccurately. When the film is formed on the surface of the object withinthe CVD chamber, the emissivity of the object is changed like a sinewave by affect of the thin film interference. As a result, intensity ofthe radiated light form the object changes like a sine wave as shown inFIG. 35, if the temperature of it doesn't change. This leas errors inmeasuring of the temperature with a radiation thermometer as shown inFIG. 36.

[0004] To measure the surface temperature of a wafer in the process offorming a thin film on the surface of the wafer (substrate), the surfacetemperature is measured by a contact method in which a sensor such as athermocouple is disposed inside the wafer stage. Alternatively, aradiation thermometer is located above the wafer surface to detect theintensity of the radiated light for a single wavelength or twowavelengths, thereby to measure the temperature. The intensity of theradiated light changes with temperature change.

[0005] On the other hand, to measure the formation amount of a thinfilm, a wafer is illuminated with light emitted from a light sourcehaving a continuous spectral distribution. Then, the interferenceintensity of the reflected light, which is changed with increase in thefilm thickness, is detected so as to measure the film thickness.

[0006] Also, an ideal waveform is obtained based on an ideal model ofthe film construction such as the number of films, the kinds of filmsand the order of formation these films. In this case, the film thicknessis determined based on the matching of the waveform with the idealwaveform.

[0007] However, the conventional surface temperature measuring methodsdescribed above give rise to serious problems. Specifically, in thecontact method, a film is unlikely to be formed in the vicinity of thethermocouple, leading to a ununiform film formation. In the method ofmeasuring the temperature by detecting the spectral intensity of theradiated light, it is impossible to measure accurately the surfacetemperature of the film. To be more specific, if the films laminated onthe substrate such as a wafer differ from each other in, for example,kind, construction and thickness, the radiated light will be repeatedlyreflected on the upper and lower surfaces of the films so as to bringabout interference. This makes it impossible to obtain a sufficientdetecting sensitivity over a measuring wavelength. It follows that it isimpossible to measure accurately the surface temperature.

[0008] On the other hand, the conventional film thickness measuringmethod described above gives rise to an additional problem.Specifically, in this method, the film thickness is calculated bydetecting how the wavelength characteristics of the reflected light arechanged compared with the illuminated light. Therefore, under such ahigh temperature as hundreds of degrees centigrade as in a filmformation process, the influence given by the radiated light is notnegligible. Consequently, the film thickness cannot be measuredaccurately.

[0009] Further, in a film formation apparatus in which a wafer isrotated at a high speed, the film formation is affected by eccentricityand planar vibration of the wafer rotation. Therefore, it is impossibleto measure the reflected light stably with a high reproducibility,making it impossible to measure accurately the film thickness.

[0010] Still further, an ideal waveform is calculated in theconventional method by using as an ideal model the construction of afilm consisting of plural layers. Thus, it is impossible to measureaccurately the film thickness unless the film construction is known inadvance.

[0011]FIG. 37 schematically shows the principle of a wafer temperaturemonitoring apparatus 1 used in, for example, a conventionalsemiconductor processing apparatus. The wafer temperature monitoringapparatus 1 comprises a He—Ne laser device 3 for irradiating asemiconductor wafer ω housed in a chamber 2 with a laser beam 6, whichis shown in FIG. 38, and a pair of CCD cameras 4 and 5 for detecting thediffracted light reflected from the semiconductor wafer co. If thesemiconductor wafer ω housed in the chamber 2 is heated to a hightemperature, the wafer ω is expanded so as to change a reflection angleθ of the diffracted light. As a result, the position at which thediffracted light 7 is detected by the CCD cameras 4 and 5 is moved inaccordance with the change in temperature. In the wafer temperaturemonitoring apparatus 1, the temperature is measured by detecting theamount of the movement of the position noted above.

[0012] However, the conventional wafer temperature monitoring apparatus1 gives rise to a problem. Specifically, as shown in FIG. 38, films n1and n2 are formed on the semiconductor wafer ω in accordance withprogress of the treatment. Also, if the temperature of the gas withinthe film formation chamber 2 is changed to form gaseous layers n3 and n4differing from each other in temperature, the diffracted light 7 isrefracted to form a diffracted light 8. As a result, the positions atwhich the diffracted light beams 7 and 8 reach the CCD camera 4 or 5 aremade different from each other by an amount of Δd. Hence, it isimpossible to distinguish the temperature change of the semiconductorwafer ω from the change in the film thickness or from the change in thetemperature of the ambient gas. It is therefore impossible to monitoraccurately the temperature.

[0013] It is very important to control the temperature of the wafersurface in the various steps such as the film formation step and theetching step employed in the manufacture of a semiconductor device. Ingeneral, a thermocouple is used as a highly reliable temperaturemeasuring means. During the manufacturing process of the semiconductordevice, a thermocouple is brought into contact with the back surface ofthe wafer or with a tool for supporting the wafer so as to perform thetemperature control. However, use of a thermocouple gives rise toproblems in terms of contamination and life of use. In addition, it isimpossible to use a thermocouple for measuring the most importanttemperature, i.e., temperature on the wafer surface at which chemicalreactions are carried out.

[0014] On the other hand, a radiation thermometer is a typical exampleof the known non-contact type thermometer. However, if the film qualityor the film thickness is changed during the process, the radiationthermometer is rendered incapable of measuring the temperature by achange in emissivity and the film interference. It should also be notedthat the radiation thermometer is for measuring high temperaturesexceeding, in general, 500° C. In other words, the radiation thermometercannot be used for measuring intermediate and low temperatures lowerthan 500° C. The thermometer cannot be used in the intermediate and lowtemperature processes such as the etching process, P-CVD process, andsputtering process.

[0015] Recently, a new method for measuring temperature is proposed, inwhich a pattern of holes formed in a wafer such as contact holes andtrenches is illuminated with a laser beam. In this method, a change inthe diffraction angle of the diffracted light is detected and thetemperature is calculated from the relationship between the diffractionangle and the temperature. In the temperature measuring method of thistype, however, it is difficult to form in advance a predeterminedpattern of holes in the wafer.

[0016] In a film thickness measuring apparatus used in a processapparatus such as a CVD apparatus for formation a thin film on asemiconductor wafer, the waveform before the film formation is taken infor every wafer to be measured. A peak is therefore obtained by usingonly the waveform of the sample. The film thickness is measured from thepeak value thus obtained.

[0017] However, the film thickness measuring apparatus of this typegives rise to a problem. Specifically, if the thickness of theunderlying film is ununiform in the case of measuring the thickness of afilm during or after formation in, for example, a CVD apparatus, themeasurement is affected by the ununiform thickness of the underlyingfilm so as to bring about a measuring error.

BRIEF SUMMARY OF THE INVENTION

[0018] An object of the first aspect of the present invention is tomeasure accurately the temperature of an object to be measured, i.e., anobject, whose emissivity is unknown or changed.

[0019] According to the first aspect of the present invention, theintensity of light radiated from the object is detected, and theintensity of the light reflected from the object when the object isilluminated with light is detected. The reflectivity of the object isobtained on the basis of the detected intensity of the reflected lightand a reference intensity of the reflected light. Further, thetemperature of the object is obtained on the basis of the emissivityobtained from the reflectivity and the intensity of the radiated light.The particular technique makes it possible to measure accurately thetemperature of the object whose emissivity is unknown or changed.

[0020] An object of the second aspect of the present invention is tomeasure accurately the surface temperature of a substrate during thefilm formation treatment and to measure accurately the film thicknessduring the film formation treatment.

[0021] According to the second aspect of the present invention, it ispossible to obtain a sufficient detecting sensitivity by obtaining anintegrated value of the radiation intensity by cumulatively adding theintensities of components of the light radiated from the substrate andhaving various wavelengths. Further, it is possible to perform themeasurement accurately because the surface temperature is calculatedfrom the integrated value on the basis of reference data having thetemperature and the integrated value correlated each other in advance.

[0022] It should also be noted that a relative intensity distribution ofradiated light, which is a ratio of a reference intensity distributionof radiated light to a measured intensity distribution of radiatedlight, is obtained and compared with a theoretical intensitydistribution of radiated light so as to offset the influence given by anoptical system. Further, it is possible to cancel the noise generatedby, for example, disturbance, making it possible to measure accuratelythe film thickness without being disturbed by noises or the like. Inother words, since it is possible in principle to reduce the noisecaused by, for example, disturbance, the measurement is less affected bynoises.

[0023] An object of the third aspect of the present invention is tomeasure accurately the temperature of a semiconductor wafer withoutbeing affected by the changes in the film thickness and in thetemperature of the ambient gas, to measure the thickness of the thinfilm formed on a wafer, and to measure simultaneously the wafertemperature and the film thickness.

[0024] According to the third aspect of the present invention, an imageformation point on a sensor is determined by an incident angle of adiffracted light on a lens. Therefore, since the image formation pointis not changed even if the incident position of the diffracted light isdeviated by, for example, refraction, the temperature can be measuredwithout being affected by refraction caused by a thin film or ambienttemperature. Further, since the intensity of the diffracted light ischanged depending on the thickness of a thin film formed on a waferbecause of the thin film interference, it is possible to measure thethickness of the thin film formed on the wafer on the basis of theintensity of the diffracted light received by a sensor.

[0025] An object of the fourth aspect of the present invention is tomeasure in a non-contact style the temperature of an object by utilizinga diffracted light without formation in advance a predetermined patternof holes in the object.

[0026] According to the fourth aspect of the present invention, thetemperature is calculated on the basis of the interval of interferencefringes formed by the light rays reflected from a pair of reflectingsurfaces of an object, making it unnecessary to form a special patternand to measure the temperature highly accurately.

[0027] An object of the fifth aspect of the present invention is tocancel the influence given by a ununiform thickness of the underlyingfilm so as to improve the accuracy in measuring the film thickness.

[0028] According to the fifth aspect of the present invention, thethickness of the uppermost layer of a film during a film formationprocess is measured in accordance with the thickness of the underlyingfilm, making it possible to measure accurately the film thicknesswithout being affected by a difference in the thickness of theunderlying film. It follows that formation of the uppermost layer can bestopped accurately at a target thickness.

[0029] Additional objects and advantages of the invention will be setforth in the description which follows, and in part will be obvious fromthe description, or may be learned by practice of the invention. Theobjects and advantages of the invention may be realized and obtained bymeans of the instrumentalities and combinations particularly pointed outhereinafter.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0030] The accompanying drawings, which are incorporated in andconstitute a part of the specification, illustrate presently preferredembodiments of the invention, and together with the general descriptiongiven above and the detailed description of the preferred embodimentsgiven below, serve to explain the principles of the invention.

[0031]FIG. 1 shows how a temperature measuring apparatus according to afirst embodiment of the present invention is used for measuring thetemperature of a semiconductor wafer on which a film is being formedwithin a CVD chamber;

[0032]FIG. 2 shows the change with time in the temperature of thesemiconductor wafer during the film formation on the wafer within theCVD chamber shown in FIG. 1;

[0033]FIG. 3 shows how a temperature measuring apparatus according to asecond embodiment of the present invention is used for measuring thetemperature of a semiconductor wafer on which a film is being formedwithin a CVD chamber;

[0034]FIG. 4 shows how a temperature measuring apparatus according to athird embodiment of the present invention is used for measuring thetemperature of a semiconductor wafer on which a film is being formedwithin a CVD chamber;

[0035]FIG. 5 shows how a temperature measuring apparatus according to afourth embodiment of the present invention is used for measuring thetemperature of a semiconductor wafer on which a film is being formedwithin a CVD chamber;

[0036]FIG. 6 shows the construction of a surface temperature measuringapparatus according to a fifth embodiment of the present invention;

[0037]FIGS. 7A and 7B are graphs showing the relationship betweentemperature and light intensity, both detected by the surfacetemperature measuring apparatus shown in FIG. 6;

[0038]FIG. 8 is a graph showing the relationship between the theoreticallight intensity and the light intensity actually measured by the surfacetemperature measuring apparatus shown in FIG. 6;

[0039]FIG. 9 shows the construction of a film thickness measuringapparatus according to a sixth embodiment of the present invention;

[0040]FIG. 10 shows the principle of measurement in the film thicknessmeasuring apparatus shown in FIG. 9;

[0041]FIGS. 11A and 11B are graphs showing the intensity distribution ofradiated light, which is measured by the film thickness measuringapparatus shown in FIG. 9;

[0042]FIG. 12A is a graph showing the relative intensity distribution ofradiated light;

[0043]FIG. 12B is a graph showing the theoretical intensity distributionof radiated light;

[0044]FIG. 13 shows the construction of a gist portion of a filmthickness measuring apparatus according to a modification of the sixthembodiment of the present invention;

[0045]FIG. 14 shows the construction of a film thickness measuringapparatus according to a seventh embodiment of the present invention;

[0046]FIGS. 15A and 15B show the intensity distribution of the reflectedlight, which is measured by the film thickness measuring apparatus shownin FIG. 14;

[0047]FIG. 16A is a graph showing a relative intensity distribution ofradiated light;

[0048]FIG. 16B is a graph showing the relationship between the filmthickness and the wavelength at which a maximal value takes place;

[0049]FIG. 17 shows the construction of a monitoring apparatus accordingto an eighth embodiment of the present invention;

[0050]FIG. 18 schematically shows the positional relationship between alens and a CCD camera incorporated in the monitoring apparatus shown inFIG. 17;

[0051]FIGS. 19A to 19C show spot images formed by a CCD cameraincorporated in the monitoring apparatus shown in FIG. 17;

[0052]FIGS. 20A and 20B show how an inclination of a semiconductor waferis corrected by using the monitoring apparatus shown in FIG. 17;

[0053]FIG. 21 shows the construction of a temperature measuringapparatus according to a ninth embodiment of the present invention;

[0054]FIGS. 22A and 22B show the principle of the temperaturemeasurement performed by the temperature measuring apparatus shown inFIG. 21;

[0055]FIG. 23 shows the principle of the temperature measurementperformed by the temperature measuring apparatus shown in FIG. 21;

[0056]FIGS. 24A and 24B show the intensity distribution of interferencefringes in the temperature measuring apparatus shown in FIG. 21 and theresult of calculation by a maximum entropy method;

[0057]FIGS. 25A to 25C show the movement of the measuring point in thetemperature measuring apparatus shown in FIG. 21;

[0058]FIGS. 26A and 26B show the movement of the measuring point in thetemperature measuring apparatus shown in FIG. 21;

[0059]FIGS. 27A and 27B show images of interference fringes in thetemperature measuring apparatus shown in FIG. 21;

[0060]FIG. 28 shows the principle of measuring the moving amount in thetemperature measuring apparatus shown in FIG. 21;

[0061]FIGS. 29A and 29B show how a measuring error is caused by a laserbeam diameter in the temperature measuring apparatus shown in FIG. 21;

[0062]FIG. 30 shows how a measuring error is caused by a lens aberrationin the temperature measuring apparatus shown in FIG. 21;

[0063]FIG. 31 shows the construction of a CVD apparatus according to atenth embodiment of the present invention;

[0064]FIG. 32 is a graph showing a first data base of the CVD apparatusshown in FIG. 31;

[0065]FIG. 33 is a graph showing a second data base of the CVD apparatusshown in FIG. 31;

[0066]FIG. 34 is a flow chart showing the procedure of formation a filmin the CVD apparatus shown in FIG. 31; and

[0067] FIGS. 35 to 38 relate to prior art, in which:

[0068]FIG. 35 shows changes in the intensity of light radiated from asemiconductor wafer and in the intensity of the reflected light during afilm formation within a CVD chamber;

[0069]FIG. 36 shows the result of the temperature measurement of asemiconductor wafer using a radiation thermometer;

[0070]FIG. 37 shows the construction of a conventional wafer temperaturemonitoring apparatus; and

[0071]FIG. 38 shows the influences given by an ambient temperature and afilm thickness in the wafer temperature monitoring apparatus shown inFIG. 38.

DETAILED DESCRIPTION OF THE INVENTION

[0072] There now follows a description of the present invention withreference to the accompanying drawings.

[0073]FIGS. 1 and 2 collectively show the first embodiment of thepresent invention. Specifically, FIG. 1 shows the construction of atemperature measuring apparatus, which is used for measuring thetemperature of a semiconductor wafer ωa during film formation on thewafer within a CVD chamber 101.

[0074] As shown in the drawing, a film is formed on the semiconductorwafer ωa, which is kept rotated, within the CVD chamber 101. A detectingterminal 105 including a lens 104 is mounted to one view port 103 on theupper surface of the CVD chamber 101. The detecting terminal 105, whichis used as a radiation spectrum detecting means for detecting thespectrum of light radiated from the semiconductor wafer ωa, is connectedto a spectroscope 107 via an optical fiber 106.

[0075] The spectrum of light radiated from the semiconductor wafer ωaand received through the lens 104 and the optical fiber 106 is detectedby a photoelectric sensor included in the spectroscope 107 and convertedin the spectroscope 107 into a signal denoting the spectrum of theradiated light. Only the spectrum of the light component having apredetermined wavelength, e.g., 800 to 900 nm, which is selected fromamong the light radiated from the semiconductor wafer ωa, is acquired bythe spectroscope 107.

[0076] On the other hand, a detecting terminal 110 including a lens 109is mounted to another view port 108 formed on the upper surface of theCVD chamber 101. The detecting terminal 101, which is used as areflected light spectrum detecting means for detecting the spectrum ofthe reflected light when the semiconductor wafer ωa is irradiated withlight, is connected to an optical fiber 111, which is branched into anoptical fiber 112 and another optical fiber 114. A halogen lamp 113 isconnected to the optical fiber 112. Also, a spectroscope 115 isconnected to the other optical fiber 114.

[0077] The light, reflected from the semiconductor wafer ωa when thewafer ωa is irradiated with light radiated from the halogen lamp 113, isreceived by the spectroscope 115 through the lens 109 and the opticalfibers 111 and 114, and the spectrum of the light reflected from thesemiconductor wafer ωa is detected by a photoelectric sensor included inthe spectroscope 115 so as to be converted into a reflected lightspectrum signal. Only the spectrum of the light component having apredetermined wavelength, e.g., 800 to 900 nm, which is selected fromamong the light radiated from the halogen lamp and the light reflectedfrom the semiconductor wafer ωa, is acquired by the spectroscope 115, asin the spectroscope 107.

[0078] The reflected light spectrum signal generated from thespectroscope 115 is supplied to a reflectance calculating section 116,to obtain a ratio of the reflected light spectrum to a referencereflected light spectrum stored in advance in the reflectancecalculating section 116. To be more specific, when a referencesemiconductor wafer (bare silicon) is used in place of the semiconductorwafer ωa, the reference semiconductor wafer is irradiated with the lightradiated from the halogen lamp 113 and the light reflected from thereference semiconductor wafer is received by the spectroscope 115through the lens 109 and the optical fibers 111 and 114 so as to obtaina spectrum of the light reflected from the reference semiconductorwafer. The reflected light spectrum thus obtained is stored in advancein the reflectance calculating section 116, as described above. Thereflectance of the semiconductor wafer ωa is obtained within thereflectance calculating section 116, from the ratio of the spectrum ofthe light reflected from the semiconductor wafer ωa to the spectrum ofthe light reflected from the reference semiconductor wafer.

[0079] The reflectance acquired in the reflectance calculating section116 is supplied to a temperature calculating section 117 which includesan emission rate calculating section 118. The emission rate is obtainedby an equation (1) in the emission rate calculating section 118 from thereflectance obtained in the reflectance calculating section 116:

E=1−R−T  (1)

[0080] where, E represents the emission rate, R represents thereflectance, and T represents the transmittance.

[0081] Then, the temperature of the semiconductor wafer ωa is obtainedby an equation (2) based on the emission rate E thus obtained and thespectrum of the radiated light detected by the spectroscope 107:

Temperature=⁴{square root}{square root over ( )}(1/σ)∫E·Rs dλ  (2)

[0082] where, σ represents the Stefan-Boltzmann constant, E representsthe emission rate, Rs represents the radiation spectrum, and λrepresents the wavelength.

[0083] Let us describe the operation of the apparatus constructed asdescribed above.

[0084] Specifically, during the film formation on the semiconductorwafer ωa which is kept rotated within the CVD chamber 101, the lightradiated from the semiconductor wafer ωa is guided to the spectroscope107 via the lens 104 of the detecting terminal 105 connected to the viewport 103 and the optical fiber 106. Only the spectrum of the lightcomponent having a wavelength of, for example, 800 to 900 nm, which isselected from among the light received by the spectroscope 107, isacquired in the spectroscope 107 so as to be converted by thephotoelectric sensor into a radiated light spectrum signal representingthe spectrum of the light radiated from the semiconductor wafer ωa.

[0085] On the other hand, the light radiated from the halogen lamp 113is guided through the optical fibers 112 and 111 and, then, the surfaceof the semiconductor wafer ωa arranged within the CVD chamber 101 isirradiated with the light radiated from the halogen lamp through thelens 109 included in the detecting terminal 110. Further, the lightreflected from the semiconductor wafer ωa is guided to the spectroscope115 through the lens 109 of the detecting terminal 110 connected to theview port 108 and through the optical fibers 111 and 114.

[0086] Only the spectrum of the light component having a wavelength of,for example, 800 to 900 nm, which is selected from among the lightreflected from the semiconductor wafer ωa, is acquired in thespectroscope 115 and converted by the photoelectric sensor into areflected light spectrum signal denoting the spectrum of the lightreflected from the semiconductor wafer ωa.

[0087]FIG. 35 shows changes in the radiated light spectrum, which isobtained by integrating the spectrum signal of the radiated light havinga wavelength of 800 to 900 nm, said signal being acquired in thespectro-scope 107, and in the reflected light spectrum, which isobtained by integrating the spectrum signal of the reflected lighthaving a wavelength of 800 to 900 nm, said signal being acquired in thespectroscope 115.

[0088] The reflected light spectrum signal generated from thespectroscope 115 is supplied to the reflectance calculating section 116.The reflectance of the semiconductor wafer ωa is obtained from a ratioof the reflected light spectrum within the spectroscope 115 to thereflected light spectrum which is stored in advance in the reflectancecalculating section 116 and is detected in the case of using a referencesemiconductor wafer. It should be noted that, where the semiconductorwafer ωa is a silicon wafer, the transmittance of light having awavelength of 800 to 900 nm is 0, with the result that the emission rateof the semiconductor wafer ωa is obtained on the basis of thereflectance, as apparent from the equation (1).

[0089] The emission rate is acquired in the temperature calculatingsection 117 by an equation (1) from the reflectance obtained in thereflectance calculating section 116. Further, the temperature of thesemiconductor wafer ωa is acquired in the temperature calculatingsection 117 by an equation (2) based on the emission rate thus obtainedand the radiated light spectrum detected by the spectroscope 107. FIG. 2shows changes with time in the temperature of the semiconductor wafer ωaduring a film formation on the semiconductor wafer ωa within the CVDchamber 101, said temperature being measured on a real time basis.

[0090] As described above, in the first embodiment of the presentinvention, the spectrum of the light radiated from the semiconductorwafer ωa is detected. Also detected is the spectrum of the lightreflected from the semiconductor wafer ωa when the semiconductor waferωa is irradiated with light. The reflectance of the semiconductor waferωa is obtained on the basis of the reflected light spectrum thusdetected and a reference reflected light spectrum. Further, thetemperature of the semiconductor wafer ωa is obtained on the basis ofthe reflectance thus obtained and the semiconductor wafer ωa. It followsthat, even if the radiated light spectrum is changed by a thin filminterference to depict a sine wave, the temperature of the semiconductorwafer ωa can be measured accurately on the real time basis without beingaffected by the sine wave-like change in the spectrum of the radiatedlight, in spite of the fact that the temperature of the semiconductorwafer ωa is being changed as in the process of forming a film on thesemiconductor wafer ωa within the CVD chamber 101. It should also benoted that the temperature of a object, whose emission rate is unknown,other than the semiconductor wafer ωa can also be measured accurately inthe first embodiment of the present invention.

[0091] Let us describe a temperature measuring apparatus according to asecond embodiment of the present invention with reference to FIG. 3.Those members of the apparatus which are common with the members of theapparatus shown in FIG. 1 are denoted by the same reference numerals soas to omit an overlapping description. The temperature measuringapparatus shown in FIG. 3 is used for measuring the temperature of alight-transmitting semiconductor wafer ωb on which a film is beingformed within the CVD chamber 101.

[0092] As shown in FIG. 3, a detecting terminal 122 including a lens 121is mounted to a view port 120 on the lower surface of the CVD chamber101 as a transmitting light spectrum detecting means for detecting thespectrum of the light transmitted through the light-transmittingsemiconductor wafer ωb. Also, a spectroscope 124 is connected to thedetecting terminal 122 through an optical fiber 123.

[0093] The spectrum of the light transmitted through the semiconductorwafer ωb is detected by a photoelectric sensor included in thespectroscope 124 and, then, converted within the spectroscope 124 into asignal denoting the spectrum of the transmitted light. Also, only thespectrum of the light component having a wavelength of, for example, 800to 900 nm, which is selected from among the light transmitted throughthe semiconductor wafer ωb, is obtained in the spectroscope 124.

[0094] The transmitted light spectrum signal generated from thespectroscope 124 is supplied to a transmittance calculating section 125to obtain a ratio of the transmitted light spectrum to a referencetransmitted light spectrum stored in advance in the transmittancecalculating section 125. To be more specific, when a referencesemiconductor wafer (bare silicon) is used in place of the semiconductorwafer ωb, the reference semiconductor wafer is irradiated with the lightradiated from the halogen lamp 113 and the light transmitted through thereference semiconductor wafer is received by the spectroscope 124through the lens 121 and the optical fibers 123 so as to obtain aspectrum of the light transmitted through the reference semiconductorwafer. The transmitted light spectrum thus obtained is stored in advancein the transmittance calculating section 125, as described above. Thetransmittance of the semiconductor wafer ωb is obtained within thetransmittance calculating section 125 from the ratio of the spectrum ofthe light transmitted through the semiconductor wafer ωb to the spectrumof the light transmitted through from the reference semiconductor wafer.

[0095] The temperature measuring apparatus of the second embodiment,which is constructed as described above, is operated as follows.Specifically, during the film formation on the semiconductor wafer ωawhich is kept rotated within the CVD chamber 101, the light radiatedfrom the semiconductor wafer ωa is guided to the spectroscope 107 viathe optical fiber 106, as in the apparatus of the first embodiment. Onlythe spectrum of the light component having a wavelength of, for example,800 to 900 nm, which is selected from among the light received by thespectroscope 107, is obtained in the spectroscope 107 so as to beconverted into a radiated light spectrum signal representing thespectrum of the light radiated from the semiconductor wafer ωa.

[0096] On the other hand, the light radiated from the halogen lamp 113is guided through the optical fibers 112 and 111 and, then, the surfaceof the semiconductor wafer ωa is irradiated with the light radiated fromthe halogen lamp 113. Further, the light reflected from thesemiconductor wafer ωa is guided again to the spectroscope 115 throughthe optical fibers 111 and 114.

[0097] Only the spectrum of the light component having a wavelength of,for example, 800 to 900 nm, which is selected from among the lightreflected from the semiconductor wafer ωa, is acquired in thespectroscope 115 and converted into a reflected light spectrum signaldenoting the spectrum of the light reflected from the semiconductorwafer ωa.

[0098] The reflected light spectrum signal generated from thespectroscope 115 is supplied to the reflectance calculating section 116so as to obtain the reflectance of the semiconductor wafer ωb from aratio of the reflected light spectrum supplied to the reflectancecalculating section 116 to a reflected light spectrum which is detectedin the case of using a reference semiconductor wafer stored in advance.

[0099] Further, the transmitted light spectrum signal generated from thespectroscope 124 is supplied to the transmittance calculating section125 to obtain the transmittance of the semiconductor wafer ωb on thebasis of a ratio of the transmitted light spectrum supplied to thesection 125 to a transmitted light spectrum stored in advance in thetransmittance calculating section 125, which is detected in the case ofusing a reference semiconductor wafer.

[0100] Then, the emission rate is obtained by an equation (1) based onthe reflectance obtained in the reflectance calculating section 116 andthe transmittance calculated in the transmittance calculating section125. Further, the temperature of the semiconductor wafer ωa is obtainedin the temperature calculating section by an equation (2) based on theemission rate thus obtained and the radiated light spectrum detected bythe spectroscope 107.

[0101] As described above, in the temperature measuring apparatusaccording to the second embodiment of the present invention, thetransmitted light spectrum when the semiconductor wafer ωb is irradiatedwith light is detected so as to obtain the transmittance of thesemiconductor wafer ωb. Then, the temperature of the semiconductor waferωb is obtained on the basis of the transmittance thus obtained as wellas the reflectance and the radiated light spectrum. It follows that thetemperature of the semiconductor wafer ωa can be measured accurately onthe real time basis during film formation on the wafer ωa within the CVDchamber 101 as in the apparatus of the first embodiment, even if thesemiconductor wafer ωb transmits light. It should also be noted that thetemperature measuring apparatus of the second embodiment permitsmeasuring the temperature of a object, whose emission rate andtransmittance are unknown, other than the semiconductor wafer ωa.

[0102]FIG. 4 shows the construction of a temperature measuring apparatusaccording to a third embodiment of the present invention. Those membersof the apparatus which are common with the members of the apparatusshown in FIG. 3 are denoted by the same reference numerals so as toavoid an overlapping description. FIG. 4 shows that the apparatus of thethird embodiment is used for measuring the temperature of asemiconductor wafer during film formation on the wafer within a CVDchamber.

[0103] As shown in FIG. 4, an on-off mechanism 130 for performing an on(closed)-off (open) operation of light such as a chopper or a shutter ismounted to the optical fiber 112 connected to the halogen lamp 113. Theon-off mechanism 130 serves to turn the light radiated from the halogenlamp 113 on and off at a predetermined interval under the control of asynchronism control section 131 which delivers a synchronous signal s toeach of the spectroscopes 115 and 124.

[0104] The spectroscope 115 serves to detect the spectrum of the lightradiated from the semiconductor wafer ωb when the on-off mechanism 130is turned on so as to shield the light radiated from the halogen lamp113 and also serves to detect the spectrum of the light reflected fromthe semiconductor wafer ωb when the on-off mechanism 130 is turned offso as to permit the semiconductor wafer ωb to be irradiated with lightradiated from the halogen lamp 113.

[0105] On the other hand, the spectroscope 124 serves to detect thespectrum of the light transmitted through the semiconductor wafer ωbwhen the on-off mechanism 130 is turned off so as to permit thesemiconductor wafer ωb to be irradiated with light radiated from thehalogen lamp 113.

[0106] The reflectance calculating section 116 receives the synchronoussignal s delivered from the synchronism control section 131. Thereflected light spectrum signal generated from the spectroscope 115 isalso supplied to the reflectance calculating section 116 when the on-offmechanism 130 is turned off so as to allow the reflectance calculatingsection 116 to obtain the reflectance of the semiconductor wafer ωbbased on a ratio of the reflected light spectrum supplied to the section116 to a reflected light spectrum stored in advance in the section 116,which is detected in the case of using a reference semiconductor wafer.

[0107] The transmittance calculating section 125 also receives thesynchronous signal s delivered from the synchronism control section 131.The transmitted light spectrum signal generated from the spectroscope124 is also supplied to the transmittance calculating section 125 whenthe on-off mechanism 130 is turned off so as to obtain the transmittanceof the semiconductor wafer ωb based on a ratio of the transmitted lightspectrum supplied to the section 125 to a transmitted light spectrumstored in advance in the section 125, which is detected in the case ofusing a reference semiconductor wafer.

[0108] The emission rate is obtained in the temperature calculatingsection 117 by equation (1) from the reflectance obtained in thereflectance calculating section 116 and the transmittance obtained inthe transmittance calculating section 125. Further, the temperature ofthe semiconductor wafer ωa is obtained in the temperature calculatingsection 117 by equation (2) based on the emission rate thus obtained andthe radiated light spectrum detected by the spectroscope 115 when theon-off mechanism 130 is turned on upon receipt of a synchronous signaldelivered from the synchronism control section 131.

[0109] There now follows a description of the operation of thetemperature measuring apparatus constructed as described above.

[0110] During film formation on the semiconductor wafer ωa which isrotated within the CVD chamber 101, the halogen lamp 113 radiates lightand the on-off mechanism 130 turns the light radiated from the halogenlamp 113 on and off at a predetermined interval under the control of thesynchronism control section 131. When the on-off mechanism 130 is turnedon to shield the light radiated from the halogen lamp 113, the lightradiated from the semiconductor wafer ωa is guided to the spectroscope115 through the optical fibers 111 and 114. Only the spectrum of thelight component having a wavelength of, for example, 800 to 900 nm,which is selected from among the light radiated from the semiconductorwafer ωa, is obtained in the spectroscope 115 so as to be converted intoa signal denoting the spectrum of the light radiated from thesemiconductor wafer ωa.

[0111] On the other hand, when the on-off mechanism 130 is turned off topermit the surface of the semiconductor wafer ωa to be irradiated withthe light radiated from the halogen lamp 113 and guided to thesemiconductor wafer ωa through the optical fibers 112 and 111, the lightreflected from the surface of the semiconductor wafer ωa is guided tothe spectroscope 115 through the optical fibers 111 and 114. Only thespectrum of the light component having a wavelength of, for example, 800to 900 nm, which is selected from among the light reflected from thesemiconductor wafer wa, is obtained in the spectroscope 115 so as to beconverted into a signal denoting the spectrum of the light reflectedfrom the semiconductor wafer ωa. In this step, the reflected lightspectrum signal generated from the spectroscope 115 when the on-offmechanism 130 is turned off, upon receipt of a synchronous signaldelivered from the synchronism control section 131, is supplied to thereflectance calculating section 116. As a result, the reflectance of thesemiconductor wafer ωb is obtained in the reflectance calculatingsection 116 from a ratio of the reflected light spectrum supplied to thesection 116 to a reflected light spectrum stored in advance in thesection 116, which is detected in the case of using a referencesemiconductor wafer.

[0112] At the same time the light, transmitted through the semiconductorwafer ωa when the on-off mechanism 130 is turned off to permit thesurface of the semiconductor wafer ωa to be irradiated with the lightradiated from the halogen lamp 113, is guided to the spectroscope 124through the optical fiber 123. Only the spectrum of the light having awavelength of, for example, 800 to 900 nm, which is selected from amongthe light transmitted through the semiconductor wafer ωa, is obtained inthe spectroscope 124 so as to be converted into a signal denoting thespectrum of the light transmitted through the semiconductor wafer ωa.

[0113] In this step, the transmitted light spectrum signal generatedfrom the spectroscope 124 when the on-off mechanism 130 is turned onupon receipt of a synchronous signal delivered from the synchronismcontrol section 131 is supplied to the transmittance calculating section125. As a result, the transmittance of the semiconductor wafer ωb isobtained from a ratio of the transmitted light spectrum supplied to thetransmittance calculating section 125 to a transmitted light spectrumstored in advance in the section 125, which is detected in the case ofusing a reference semiconductor wafer.

[0114] Then, the emission rate is obtained in the temperaturecalculating section 117 by equation (1) from the reflectance obtained inthe reflectance calculating section 116 and the transmittance obtainedin the transmittance calculating section 125. Further, the temperatureof the semiconductor wafer ωa is obtained in the temperature calculatingsection 117 by an equation (2) on the basis of the emission rate thusobtained and the radiated light spectrum detected by the spectroscope115 when the on-off mechanism 130 is turned on upon receipt of asynchronous signal s delivered from the synchronism control section 131.

[0115] As described above, in the temperature measuring apparatusaccording to the third embodiment of the present invention, the lightradiated from the halogen lamp 113 is turned on or off by the on-offmechanism 130 so as to permit the reflected light and the radiated lightfrom the semiconductor wafer ωb to be alternately received insynchronism with the on-off function of the light radiated from thehalogen lamp 113. The temperature of the semiconductor wafer ωb isobtained on the basis of the reflected light spectrum and the radiatedlight spectrum. Needless to say, the apparatus according to the thirdembodiment of the present invention produces effects similar to thoseproduced by the apparatus of the second embodiment. In addition, theapparatus of the third embodiment can be simplified, compared with theapparatus of the second embodiment, because the detecting terminal 105,the optical fiber 106 and the spectroscope 107, which are included inthe apparatus of the second embodiment, need not be used in theapparatus of the third embodiment.

[0116] The above description of the third embodiment covers the casewhere the temperature measuring apparatus is used for measuring thetemperature of the semiconductor wafer ωb which transmits light. If theapparatus of the third embodiment is used for measuring the temperatureof the semiconductor wafer ωa having a light transmittance ofsubstantially 0, e.g., less than 0.01%, it is possible to furthersimplify the apparatus by omitting the detecting terminal 122, theoptical fiber 123, the spectroscope 124 and the transmittancecalculating section 125.

[0117] Let us describe a temperature measuring apparatus according to afourth embodiment of the present invention with reference to FIG. 5.Those members of the apparatus shown in FIG. 5 which are common with themembers of the apparatus shown in FIG. 1 are denoted by the samereference numerals so as to avoid an overlapping description. Theapparatus shown in FIG. 5 is used for measuring the temperature of thesemiconductor wafer ωa during film formation on the wafer ωa within theCVD chamber.

[0118] In the apparatus shown in FIG. 5, a device consisting of aninterference filter 140 and a photoelectric sensor 141 is used in placeof the spectroscope 107 shown in FIG. 1. Also, a device consisting of aninterference filter 142 and a photoelectric sensor 143 is used in placeof the spectroscope 115 shown in FIG. 1. Each of these interferencefilters 140 and 142 selectively transmits the light component having awavelength of, for example, 800 to 900 nm.

[0119] There now follows a description of the operation of thetemperature measuring apparatus of the construction described above.

[0120] Specifically, the light radiated from the semiconductor wafer ωaduring film formation thereon within the CVD chamber 101 is guided tothe interference filter 140 through the optical fiber 106. Theinterference filter 140 selectively transmits the light component havinga wavelength of, for example, 800 to 900 nm, which is selected fromamong the light radiated from the semiconductor wafer ωa. The lightcomponent transmitted through the interference filter 140 is convertedby the photoelectric sensor 141 into a signal denoting the intensity ofthe light radiated from the semiconductor wafer ωa.

[0121] On the other hand, the light radiated from the halogen lamp 113is guided by the optical fibers 112 and 111 so as to have the surface ofthe semiconductor wafer ωa irradiated with the light radiated from thehalogen lamp 113. The light reflected from the semiconductor wafer ωa isguided to the interference filter 142 through the optical fibers 111 and114. The interference filter 142 selectively transmits the lightcomponent having a wavelength of, for example, 800 to 900 nm, which isselected from among the light reflected from the semiconductor wafer ωa.The light component transmitted through the interference filter 142 isconverted by the photoelectric sensor 143 into a signal denoting theintensity of the light reflected from the semiconductor wafer ωa.

[0122] The reflected light intensity signal generated from thephotoelectric sensor 143 is supplied to the reflectance calculatingsection 116. The reflectance of the semiconductor wafer ωa is obtainedin the reflectance calculating section 116 from a ratio of the reflectedlight intensity supplied to the section 116 to a reflected lightintensity stored in advance in the section 116, which is detected in thecase of using a reference semiconductor wafer.

[0123] The emission rate is obtained in the temperature calculatingsection 117 by an equation (1) from the reflectance obtained in thereflectance calculating section 116. Further, the temperature of thesemiconductor wafer ωa is obtained in the temperature calculatingsection 117 by an equation (2) based on the emission rate thus obtainedand the radiated light intensity signal generated from the photoelectricsensor 141.

[0124] Needless to say, the temperature measuring apparatus according tothe fourth embodiment produces the effects similar to those produced bythe apparatus of the first embodiment. In addition, the apparatus of thefourth embodiment can be manufactured at a lower cost because theinterference filters 140 and 142 used in the fourth embodiment arecheaper than the spectroscopes 107 and 115 used in the apparatus of thefirst embodiment.

[0125] To reiterate, the interference filters 140 and 142 are used inthe apparatus of the fourth embodiment in place of the spectroscopes 107and 115. Likewise, interference filters can be used in each of thesecond and third embodiments in place of the spectroscopes 107, 115 and124.

[0126] As described above, the temperature measuring method and thetemperature measuring apparatus according to the first to fourthembodiments of the present invention make it possible to measureaccurately the temperature of a object whose emission rate is unknown orwhose emission rate is changed.

[0127]FIG. 6 shows the construction of a surface temperature measuringapparatus 210 according to a fifth embodiment of the present invention.

[0128] As shown in the drawing, the surface temperature measuringapparatus 210 comprises a stage 211 for holding a semiconductor waferωc, a lens 212 aligned with the wafer ωc to converge the light radiatedfrom the wafer ωc, an optical fiber 213 having one end aligned with thelens 212 for guiding the radiated light collected by the lens 212, aspectroscope 214 aligned with the other end of the optical fiber 213 forsubjecting the light having a predetermined range of wavelength to aspectroscopic analysis for every predetermined wavelength step, an arraysensor 215 mounted to the spectroscope 214 for detecting the intensityof the spectroscopically analyzed light for every wavelength step so asto generate the light intensity as an integrated value, a signalprocessing circuit 216 for collecting the signal generated from thearray sensor 215 so as to subject the collected signal to an A/Dconversion, and a computer 217 receiving the output signal generatedfrom the signal processing circuit 216 for calculating the intensitydistribution of the radiated light based on the integrated value of thelight intensity. On the other hand, a memory section 218 storing a tableconsisting of plural reference data is connected to computer 217.Incidentally, a heater 211 a is mounted under the wafer ωc.

[0129] In the surface temperature measuring apparatus 210 of theconstruction described above, the surface temperature of a film formedon a wafer ωc during a film forming process is measured as follows.Specifically, the light radiated from the surface of the wafer ωcdisposed on the wafer stage 211 and heated by the heater 211 a isconverged by the lens 212 and, then, guided to the spectroscope 214through the optical fiber 213. In the spectroscope 214, the lightspectroscopically analyzed for every predetermined wavelength step isguided to the array sensor 215. In the array sensor 215, the integratedvalue of the light intensity of a predetermined wavelength step width isdetected for every sensor. The integrated value is subjected to an A/Dconversion in the signal processing circuit 216, and the A/D convertedsignal is supplied to the computer 217.

[0130] In the computer 217, the wavelength distribution Q (d, t, λ) ofthe radiated light is calculated on the basis of the integrated value.Further, a whole wavelength intensity integrated value G (d, t)=∫Q(d, t,λ)dλ, in which the range of integration is used as the whole wavelength,is calculated on the basis of the wavelength distribution Q (d, t, λ).

[0131] The whole wavelength intensity integrated value G is standardizedon the basis of the table stored in advance in the memory section 218depending on the material, construction and thickness of the film.

[0132] There now follows a description of the table. Specifically, theemission rate is changed depending on the material, construction andthickness of the film. Therefore, the relation of the whole wavelengthintensity integrated value G to the surface temperature of the object isrepresented by a curve as shown in, for example, FIG. 7A, said curvedenoting different absolute amounts of the integrated value. Suppose,for example, the standardization with the integrated value G_(ref)=G (d,τ) at τK (Kelvin temperature). In this case, Gk=G(d, t)/G_(ref).

[0133] Incidentally, the reference data G_(ref) is corrected in advancewith τK by, for example, a contact method depending on the material,construction and thickness of the film. In this case, the standardintegrated value Gk depicts the same curve relative to the temperatureindependent of the material, construction and thickness of the film, asshown in FIG. 7B. It follows that, if it is possible to presenttheoretically the standard integrated value characteristics, the surfacetemperature of the target film can be estimated from the value of thestandard integrated value Gk. In other words, the surface temperature ofa film of every material, construction and thickness can be obtained byacquiring in advance the reference value G_(ref) in accordance with thematerial, construction and thickness of the film so as to prepare atable.

[0134] On the other hand, the blackbody radiation theory indicates thatthe radiated light distribution of a blackbody can be given by:

E=C 1/λ⁵/(exp(C 2/λτ)−1)

[0135] where C1 represents a first radiation constant (2πhc²), C2represents a second radiation constant (ch/k), λ represents awavelength, h represents the Planck's constant, k represents theBoltzmann constant, and c represents the speed of light.

[0136] If E is integrated over the whole wavelength, the so-calledStefan-Boltzmann law of:

Esb=στ ⁴,

[0137] where σ represents the Stefan-Boltzmann constant (2π⁵·k⁴/15c³/h³)is obtained.

[0138] If standardized by the theoretical integrated value Esb(τK) atτK, a standardized theoretical integrated value Ek=Esb/Esb(τK) isobtained. Ek is proportional to the fourth power of the surfacetemperature.

[0139] As shown in FIG. 8, the standard integrated value Wk calculatedfrom the actually measured values well conforms with the standardtheoretical integrated value Ek derived from the blackbody radiationtheory, making it possible to estimate the surface temperature of thefilm corresponding to the standard integrated value Wk from thetheoretical curve Ek.

[0140] The surface temperature measuring apparatus 210 of the fifthembodiment described above permits measuring, highly accurately, thesurface temperature of the wafer ωc during the film forming process.Also, the surface temperature can be measured highly accurately even ifthe material, construction and thickness of the wafer ωc are changed.

[0141] In the fifth embodiment described above, the whole wavelengthregion is integrated. However, the scope of integration can be limitedto a predetermined wavelength range. To be more specific, the actualradiation spectroscopy is strongly affected by the sensitivity of themeasuring system and the optical properties of the object. Particularly,in the wavelength region having a low measuring sensitivity, theradiation spectroscopic intensity is measured unduly low, compared withthe theoretical value, making it impossible to calculate the surfacetemperature accurately. Also, the optical characteristics of the objectshould also be considered. For example, a Si wafer exhibits atransmittance of about 100% in an infrared region having a wavelengthexceeding 1 μm, with the result that, if the wafer ωc is heated, thetemperature of the heater 211 a tends to be erroneously measured as thesurface temperature of the wafer ωc.

[0142] In order to avoid the above-noted difficulty, it is possible toobtain the intensity integrated value by limiting the wavelength regionto the region within which the measurement is not affected by thesensitivity characteristics of the measuring system and the opticalcharacteristics of the object so as to calculate the surfacetemperature. In other words, the theoretical formula corresponding toEsb is: Esb=∫Edλ (scope of integration is λ1≦λ≦λ2). This indicates thatthe temperature can be measured by a method similar to the method of thefirst embodiment of the present invention. It follows that theinfluences given by the sensitivity characteristics of the measuringsystem and the optical characteristics of the object can be suppressedto a minimum level by limiting the wavelength region so as to measurethe temperature highly accurately.

[0143]FIG. 20 shows the construction of a film forming amount measuringapparatus 220 according to a sixth embodiment of the present invention.As shown in the drawing, the film forming amount measuring apparatus 220comprises a wafer stage 221 for holding a wafer (substrate) ωc, a lens222 aligned with the wafer ωc for collecting the light radiated from thewafer ωc, an optical fiber 223 having one end aligned with the lens 222to guide the radiated light collected by the lens 222, a spectroscope224 aligned with the other end of the optical fiber 223 for subjectingthe light having a wavelength falling within a predetermined range to aspectroscopic analysis for every wavelength step, an array sensor 225mounted to the spectroscope 224 for detecting the intensity of the lightsubjected to the spectroscopic analysis for every wavelength step so asto generate an integrated value of the light intensity, a signalprocessing circuit 226 receiving the signal generated from the arraysensor 225 so as to subject the received signal to an A/D conversion,and a computer 227 for calculating the intensity distribution of theradiated light based on the integrated value of the light intensitysupplied from the signal processing circuit 226. A memory section 228storing a table consisting of plural reference data is connected to thecomputer 227. Also, a heater 221 a is mounted at a bottom portion of thewafer stage 221.

[0144] The film forming amount measuring apparatus 220 of theconstruction described above measures a film forming amount d on thewafer ωc during a film forming process as follows. Specifically, thelight radiated from the surface of the wafer ωc disposed on the waferstage 221 and heated by the heater 221 a is collected by the lens 222and, then, guided to the spectroscope 224 through the optical fiber 223.In the spectroscope 224, the light spectroscopically analyzed for everypredetermined wavelength step is guided to the array sensor 225. In thearray sensor 225, the integrated value of the light intensity of apredetermined wavelength step width is detected for every sensor. Theintegrated value is subjected to an A/D conversion in the signalprocessing circuit 226, and the A/D converted signal is supplied to thecomputer 227 so as to calculate the radiated light distribution. Theparticular operation is carried out immediately before the filmformation and during the film formation.

[0145]FIG. 10 is for explaining the reference radiated lightdistribution A_(o) obtained from the wafer ωc immediately before thefilm formation and the actually measured radiated light distribution Aobtained from the wafer ωc during the film formation. Specifically, thereference radiated light distribution A_(o) is represented by:

A _(o)(d, t, λ)=T _(n−1)(T _(n−2)( . . . T 1(Ra(t, λ)) . . . )

[0146] When the radiated light Ra (t, λ) is transmitted through thefilms formed on the wafer ωc, i.e., the lowermost film to (n−1)-th film,the radiated light Ra (t, λ) is multiply reflected by the films formedon the wafer ωc. The influences given by the multiple reflections aretaken into consideration in the reference radiated light distributionA_(o) given above. FIG. 11A shows the reference radiated lightdistribution A_(o).

[0147] On the other hand, the actually measured radiated lightdistribution A is represented by:

A(d, t, λ)=T _(n)(T _(n−1)(T 1(Ra(t, λ)) . . . )

[0148] In this case, the influences given by the multiple reflections,which take place when the light Ra (t, λ) radiated from the wafer ωc istransmitted through the films (the lowermost film to the uppermost film)formed on the wafer ωc, is taken into consideration. FIG. 11B shows theactually measured radiated light distribution A. Curves α1, α2, and α3shown in FIG. 11B represent the actually measured radiated lightdistributions at different film forming amounts.

[0149] It should be noted that, in a relative radiated lightdistribution B (d, t, λ), which is a ratio of the actually measuredradiated light distribution A (d, t, λ) to the reference radiated lightdistribution A_(o), i.e., A (d, t, λ)/A_(o) (d, t, λ), the influenceappears on the uppermost film (n-th film) alone, as shown in FIG. 12A.Incidentally, the influences given by the characteristics of the opticalsystem such as the optical fiber 223 or the spectroscope 224 and by thenoise derived from the disturbance are canceled by the arithmeticoperation for conversion into the relative radiated light distribution B(d, t, λ) so as to improve the measuring accuracy of the film formingamount d.

[0150] Then, the film forming amount d is calculated by allowing therelative radiated light distribution B to match a theoretical radiatedlight distribution Br. To be more specific, if the refractive index N(n, k) of the uppermost film (n-th film) is known, the theoreticalradiated light distribution Br (d, t, λ) showing the influences given bythe uppermost film alone can be calculated from a single layertransmitted light theory in view of the repetition. Therefore, if thetheoretical radiated light distribution Br is matched with the relativeradiated light distribution B (d, t, λ), it is possible to estimate thefilm forming amount d of the uppermost film during the film formingprocess. As a matching method, there is a method of detecting thetheoretical radiated light distribution Br (d, t, λ) which minimizes theabsolute value of the difference K between the relative radiated lightdistribution B and the theoretical radiated light distribution amountBr, i.e., K=B (d, t, λ)−Br (d, t, λ).

[0151] Since the actual splitting of the radiated light is stronglyaffected by the sensitivity of the measuring system, the intensity ofthe split radiated light tends to be measured unduly low, compared withthe theoretically calculated value, in the wavelength region of a lowmeasuring sensitivity, making it difficult to calculate accurately thefilm forming amount. In this case, it is possible to estimate the filmforming amount from the wavelength shifting amount of the intensitywaveform maximal value by utilizing the characteristic that the waveformdenoting the intensity of the split radiated light is shifted toward alonger wavelength side. This method is very effective against theinfluences given by, for example, the change in sensitivity of themeasuring apparatus.

[0152] The film forming amount measuring apparatus 220 of the sixthembodiment described above makes it possible to measure highlyaccurately the film forming amount of the uppermost film during filmformation on the wafer ωc. Also, the film forming amount can be measuredhighly accurately by utilizing the radiated light even under thecondition that the wafer ωc is rotated at a high speed, which isunsuitable for measuring the reflected light. It should also be notedthat, if the film forming amount measuring apparatus 220 is mounted in afilm forming apparatus and the film formation is stopped when the filmforming amount reaches a predetermined value, the end point of the filmformation can be controlled in the film forming apparatus.

[0153]FIG. 13 shows an essential portion of a film forming amountmeasuring apparatus 230 according to a modification of the film formingamount measuring apparatus 220 shown in FIG. 9. Those members of theapparatus 230 which are common with the members of the apparatus shownin FIG. 9 are denoted by the same reference numerals so as to avoid anoverlapping description. The film forming amount measuring apparatus 230differs from the apparatus 220 in that the film forming amount ismeasured at plural measuring points. Therefore, a lens 231 a, an opticalfiber 232 a, a spectroscope 233 a, and an array sensor 234 a arearranged in parallel with a lens 231 b, an optical fiber 232 b, aspectroscope 233 b, and an array sensor 234 b, respectively.

[0154]FIG. 14 shows the construction of a film forming amount measuringapparatus 240 according to a seventh embodiment of the presentinvention. As shown in the drawing, the film forming amount measuringapparatus 240 comprises a wafer stage 241 for holding a wafer(substrate) ωc, a lens 242 aligned with the wafer ωc for collecting thelight radiated from the wafer ωc, an optical fiber 243 having one endpositioned to face the lens 242 for guiding the radiated light collectedby the lens 242, a spectroscope 244 positioned to face the other end ofthe optical fiber 243 for splitting the light having a wavelengthfalling within a predetermined range for every wavelength step, an arraysensor 245 mounted to the spectroscope 244 for detecting the intensityof the split light for every wavelength step so as to generate anintegrated value of the light intensity, a signal processing circuit 246for collecting the signal generated from the array sensor 245 so as tosubject the collected signal to an A/D conversion, and a computer 247receiving the output signal of the signal processing circuit 246 forcalculating the intensity distribution of the radiated light based onthe integrated value of the light intensity. A memory section 248storing a table consisting of plural reference data is connected to thecomputer 247. Incidentally, a heater 241 a is mounted at a bottomportion of the wafer stage 241.

[0155] On the other hand, a half mirror 250 is arranged between the lens242 and the optical fiber 243. The half mirror 250 is irradiated withthe light source 252 so as to permit the wafer stage 241 to beirradiated with the light reflected from the half mirror 250. Further, alight source lighting circuit 253 is connected to the light source 252.

[0156] In the film forming amount measuring apparatus 240 of theconstruction described above, the film forming amount d on the wafer ωcduring the film forming process is measured as follows. The measurementis performed in advance before the film formation. Specifically, thelight source 252 is turned on so as to permit the wafer ωc to beirradiated with the light radiated from the light source 252 through thelens 251 and the half mirror 250. The light is reflected from thesurface of the wafer ωc. On the other hand, light is radiated from thewafer ωc disposed on the wafer stage 241 and heated by the heater 241 a.The reflected light and radiated light are collected by the lens 242 andguided to the spectroscope 244 through the optical fiber 243. In thespectroscope 244, the light split for every predetermined wavelengthstep is guided to the array sensor 245. In the array sensor 245, theintegrated value of the light intensity of a predetermined wavelengthstep width is detected by every sensor. The integrated value thusdetected is subjected to an A/D conversion in the signal processingcircuit 246 and, then, supplied to the computer 247.

[0157] Obtained in the computer 247 is a first intensity distribution P1(d, t, λ) of the split light including both the reflected light and theradiated light. On the other hand, the radiated light alone from thewafer ωc is similarly measured by turning off the light source 252 so asto obtain a second intensity distribution P2 (d, t, λ) of the splitlight.

[0158] A difference L_(o) between the first intensity distribution P1 ofthe split light and the second intensity distribution P2 of the splitlight represents a reference intensity distribution of the reflectedlight alone, which is stored in the memory section 248. Incidentally,the difference L_(o) is equal to R_(n−1) (R_(n−2) ( . . . R1 (S(λ)·J(λ)). . . )). The formula indicates that the product between the wavelengthdistribution S (λ) of the light source 252 and the influences J (λ) ofthe illumination optical system and the light receiving optical systemis modified by the multiple reflection of the light by the films formedon the wafer ωc (i.e., the lowermost film (1) to the (n−1)-th film).

[0159] Then, the film formation process is started. In this step, thelight source 252 is turned on and the light beams radiated and reflectedfrom the wafer ωc are similarly measured so as to obtain a thirdintensity distribution P3 (d, t, λ) of the split light. Further, thelight source 252 is turned off, and the light beam radiated from thewafer ωc is measured similarly so as to obtain a fourth intensitydistribution P4 (d, t, λ) of the split light.

[0160] A difference L between the third intensity distribution P3 of thesplit light and the fourth intensity distribution P4 of the split lightrepresents an actually measured intensity distribution of the reflectedlight. The difference L is equal to R_(n) (R_(n−1) ( . . . R1(S(λ)·J(λ)) . . . )). The formula indicates that the product between thewavelength distribution S (λ) of the light source 252 and the influencesJ (λ) of the illumination optical system and the light receiving opticalsystem is modified by the multiple reflection of the light by the filmsformed on the wafer ωc (i.e., the lowermost film (1) to the uppermostfilm (n)).

[0161]FIG. 16A shows the actually measured intensity distribution of thereflected light. Curves β1, β2 and β3 shown in FIG. 16A represent theactually measured wavelength distributions at different film formingamounts. On the other hand, FIG. 12A shows a relative intensitydistribution F (d, t, λ) of the reflected light, which is a ratio of theactually measured intensity distribution L (d, t, λ) of the reflectedlight to the reference intensity distribution L_(o) (d, t, λ) of thereflected light, i.e., F (d, t, λ)=L (d, t, λ)/ L_(o) (d, t, λ). Therelative intensity distribution F (d, t, λ) of the reflected lightrepresents the influence given by the uppermost film (n) alone.

[0162] It should be noted that the influences given by thecharacteristics of the optical system such as the optical fiber 243 andthe spectroscope 244 and the noise derived from the disturbance arecanceled by the arithmetic operation for conversion into the relativeintensity distribution F (d, t, λ) of the reflected light, leading to animproved measuring accuracy of the film forming amount d.

[0163] Then, the film forming amount d is calculated by comparing therelative intensity distribution F of the reflected light with referencedata (reference intensity distribution of the reflected light) F_(ref).The reference data F_(ref) denotes the calculated value obtained by atheoretical calculation of the thin film interference or the actuallymeasured value in the case where a film is formed in advance under thesame film forming conditions. In any case, the relationship between thereference data F_(ref) and the film forming amount d is quantitativelyknown.

[0164] The signal F denoting the influence of the uppermost film (n)alone is dependent on the film forming amount of the uppermost filmwhich is being laminated. It should be noted that the relative reflectedlight distribution F is shifted toward the longer wavelength side withan increase in the film forming amount. Therefore, if attention is paidto the maximal value of the relative reflected light distribution F soas to obtain the wavelength shift amount thereof, the thickness d of theuppermost film can be estimated by comparing the wavelength shift amountwith the reference data F_(ref.) It follows that the film forming amountof the uppermost film can be measured accurately without relying on theconstruction of the underlying film.

[0165] As described above, the film forming amount measuring apparatus240 according to the seventh embodiment of the present invention makesit possible to measure highly accurately the film forming amount of theuppermost film formed on the wafer ωc during the film forming process onthe wafer ωc. Also, the thickness of the uppermost film can be measuredeasily without relying on the construction of the underlying film of thewafer ωc. Further, the film thickness can be measured highly accuratelywhile eliminating the influences given by the sensitivitycharacteristics and the optical characteristics of the object.Incidentally, a film forming apparatus capable of controlling the endpoint of the film formation can be provided by mounting the film formingamount measuring apparatus 240 in the film forming apparatus to permitthe film formation to be stopped when a predetermined film formingamount is reached.

[0166]FIG. 17 schematically shows a monitoring apparatus 310 accordingto an eighth embodiment of the present invention. As shown in thedrawing, the monitoring apparatus 310 comprises a He—Ne laser device 312for irradiating a semiconductor wafer ωd housed in a film formingchamber 311 with a laser beam Σ, a pair of CCD cameras 313, 314 fordetecting the diffracted light reflected from the semiconductor waferωd, lenses 315, 316 aligned between the semiconductor wafer ωd and eachof the CCD cameras 313, 314, and an arithmetic section 317 forperforming arithmetic operations based on the output signals generatedfrom the CCD cameras 313, 314 as described later herein.

[0167] The pickup faces 313 a, 314 a of the CCD cameras 313, 314 arepositioned at the focal length f of the lenses 315, 316. Also, regularfine patterns are formed on the surface of the semiconductor wafer ωd.

[0168] The temperature of the semiconductor wafer ωd is measured by themonitoring apparatus 310 as follows. Specifically, the semiconductorwafer ωd is irradiated with the laser beam Σ emitted from the He—Nelaser device 312. The laser beam Σ is reflected as a diffracted light Ψat an angle conforming with the distance of the pattern formed on thesemiconductor wafer ωd.

[0169] The diffracted light Ψ is incident on each of the lenses 315, 316at an angle η so as to be collected and forms spot images Λ1, Λ2 on theCCD cameras 313, 314, respectively. It should be noted that, since thediffracted light Ψ is collected by the lenses 315, 316, the positions atwhich the spot images Λ1, Λ2 are formed are deviated by an amount of fΔηfrom the focus C of the lenses 313, 314.

[0170] To be more specific, the spot images Λ1, Λ2 on the CCD cameras313, 314 are formed at the positions conforming with the angle η atwhich the diffracted light Ψ is incident on the lenses 315, 316regardless of the positions at which the diffracted light Ψ is incidenton the lenses 315, 316. It follows that the positional deviation causedby the refraction of the diffracted light Ψ depending on the thin filmand the ambient temperature is rendered negligible.

[0171]FIGS. 19A to 19C show the positions of the spot images Λ1, Λ2 at300° C., 200° C. and 100° C., respectively. Position signals of thesespot images Λ1, Λ2 are supplied to the arithmetic section 317. Thedistance δ between the spot images Λ1, Λ2 is calculated in thearithmetic section 317 based on these position signals, and thetemperature of the semiconductor wafer ωd is calculated from thedistance δ.

[0172] It should also be noted that the intensity of the diffractedlight Ψ is changed to depict a sine wave in accordance with changes inthe thickness of the film formed on the semiconductor wafer ωd.Therefore, the thickness of the film formed on the wafer ωd can also bemeasured simultaneously by measuring the intensity of the spot imagesformed on the CCD cameras 313, 314.

[0173]FIGS. 20A and 20B cover the case where the object of thesemiconductor wafer ωd is tilted. If the semiconductor wafer ωd istilted, the positions of the spot images Λ1, Λ2 are deviated. However,the two sensors are similarly affected by this inclination, with theresult that the distance δ between the spot images Λ1, Λ2 is leftunchanged so as to cancel the tilt of the semiconductor wafer ωd. Itfollows that the temperature can be measured accurately.

[0174] As described above, in the monitoring apparatus 310 of the eighthembodiment, the diffracted light Ψ is collected to form spot images Λ1,Λ2 on the pickup faces of the CCD cameras 313, 314 in accordance withthe incident angle at the lenses 315, 316. Also, the influences given bythe thickness of the film formed on the semiconductor wafer ωd and bythe change in the ambient temperature are canceled by measuring thedistance between these spot images Λ1, Λ2 so as to decrease themeasuring error. It follows that the temperature of the wafer and thethickness of the film formed on the wafer can be measured without beingaffected by the refraction dependent on the film thickness and theambient temperature.

[0175]FIG. 21 shows the construction of a temperature measuringapparatus 410 according to a ninth embodiment of the present invention.As shown in the drawing, the temperature measuring apparatus 410comprises a detecting section 420, an arithmetic section 430 and acorrecting section 440.

[0176] The detecting section 420 consists of a laser oscillator 421 foroscillating, for example, a He—Ne laser beam for irradiating a wafer ωe,a prism (optical system for determining position) 422 for shifting anoptical path for moving the laser beam in parallel, a driving mechanism423 such as a pulse motor for rotating the prism 422 in two directions,a CCD camera (light detecting section) 424 for observing interferencefringes, and two lenses (optical system for correcting changes) 425, 426for guiding the interference fringes into the CCD camera 424. The CCDcamera 424 and the lenses 425, 426 are integrally incorporated in anoptical cylinder 427 having a black light absorber mounted to the innersurface thereof.

[0177] The prism 422 is rotated to permit the laser beam L to be shiftedin parallel so as to move the irradiating point from M1 to M2, asdenoted by, for example, a broken line Q in FIG. 21. Therefore, thetemperature can be measured at many points on the wafer ωe.Incidentally, the CCD camera 424 includes a light receiving face 424 a,as shown in FIG. 22A. Also, a filter 424 b capable of transmitting thelight having a wavelength equal to that of the laser beam L is arrangedin front of the light receiving face 424 a of the CCD camera 424.

[0178] On the other hand, the lenses 425, 426 perform the function asdescribed in the following. Specifically, the lenses 425, 426 permit theinterference fringes to be kept incident on the stationary CCD camera424 even if the measuring point is changed. For example, in the case ofusing a lens having a focal length of 100 mm, the interference fringesincident on the lens 425 are kept incident on a predetermined point ofthe CCD camera 424 by the arrangement shown in FIG. 21, in which thedistance between the irradiating point on the wafer ωe and the lens 425is 200 mm, the distance between the two lenses 425 and 426 is 300 mm,and the distance between the lens 426 and the CCD camera 424 is 200 mm.It should be noted that a solid line B shown in FIG. 21 represents theinterference fringes when the wafer we is irradiated with the laser beamL at the irradiating point M1. Also, a broken line S represents theinterference fringes when the wafer ωe is irradiated with the laser beamQ at the irradiating point M2.

[0179] The arithmetic section 430 consists of a PM driver 431 fordriving a pulse motor 423, a P1/O-1/F 432 for transmitting a commandsignal to the PM driver 431, an image processing I/F 433 for receivingthe picture image caught by the CCD camera 424 and for displaying thereceived picture image on a display 435, which is referred to later, aCPU 434 for collectively controlling the image processing operation, thearithmetic operation, etc., and the display 435 for displaying thepicture image.

[0180] Further, the correcting section 440 includes a CCD camera 441, animage processing board 442 for processing the image signal generatedfrom the CCD camera 441, and a beam diameter controller 443.

[0181] The surface temperature of the wafer ωe is measured by thetemperature measuring apparatus 410 of the construction described aboveas follows. Specifically, a pair of concave portions P1, P2 of theconcave and convex pattern P on the surface of the wafer ωe areirradiated with the laser beam L emitted from the laser oscillator 421,as shown in FIG. 22. Incidentally, FIG. 22 schematically shows thephenomenon taking place when the laser beam L is incident on the concaveand convex pattern P within an optional range. As shown in FIG. 22,diffracted light beams K1, K2 are generated from the concave portionsP1, P2 so as to form interference fringes B at the intersection betweenthe diffracted light beams K1 and K2. The interference fringes B thusformed are caught by the CCD camera 424 so as to obtain an image of theinterference fringes within the range of the light receiving face 424 a.

[0182]FIG. 22B shows an image of the interference fringes obtained bydetecting the interference fringes B with the CCD camera 424 when thepattern P is irradiated with the laser beam L. In this example, theconcave portions P1, P2 are oblong and, thus, the images of theinterference fringes are rendered oblong. This is caused by thephenomenon that the diffracted light beams K1, K2 are expanded ininverse proportion to the lengths of the concave portions P1, P2.Therefore, the interference fringes B are expanded in the direction ofthe shorter side (X-direction), as shown in the drawing.

[0183] Let us describe the relationship between the interference fringesB and the temperature of the wafer ωe. If the wafer heated, thesubstance forming the wafer ωe is expanded so as to increase thedistance between the adjacent patterns P, as shown in, for example, FIG.23. As a result, the initial cross point N1 is moved to a point N2positioned away from the wafer ωe, as shown in FIG. 23. Therefore, wherethe CCD camera 424 is stationary, a special behavior is observed as ifthe interference fringes B approach the CCD camera 424. It follows thatthe number of interference fringes B incident on the CCD camera 424 isincreased so as to cause the distance between the adjacent fringes ofthe picture image of the interference fringes on the CCD camera 424 tobe narrowed. In other words, the temperature change of the wafer ωe iscorrelated with the reduction in the distance between adjacent fringesof the interference fringes B, making it possible to obtain the changein temperature by detecting the change in the distance between adjacentfringes of the interference fringes B.

[0184] Incidentally, if the pitch of the pattern P and the wavelength ofthe laser beam L at a certain temperature are known, the distancebetween adjacent fringes of the interference fringes B can be calculatedfrom the distance between the wafer ωe and the CCD camera 424, making itpossible to identify the absolute value of the wafer temperature.

[0185] There now follows a description of how to calculate the distancebetween adjacent fringes of the interference fringes B. FIG. 24A is agraph showing the light intensity distribution in an X-direction of thepicture image of the interference fringes B. In this graph, the numberof picture elements in an X-direction of the CCD camera 424 is set at512, and the light intensities in a Y-direction are added for eachpicture element in the X-direction. As shown in the drawing, the lightintensity distribution in a planar direction forms a sine wave, and thedistance between adjacent maximal values corresponds to the distancebetween adjacent fringes of the interference fringes B. It is certainlypossible to obtain the change in temperature by simply calculating thechange in the distance between adjacent maximal values. In this case,however, the resolution is dependent on the pitch of the pictureelements of the CCD camera 424.

[0186] For improving the accuracy of the calculation, the change infrequency of the sine wave is calculated. To be more specific, thechange in frequency is inversely proportional to the change in thedistance between adjacent fringes and, thus, the temperature isproportional to the frequency. In other words, the frequency isincreased with increase in the temperature. FIG. 24B shows that thefrequency is calculated to be, for example, 16.64179 Hz by the maximumentropy method (MEM), which is an example of the frequency analysis.

[0187] The movement of the measuring point accompanying the change intemperature is corrected in the present invention. Specifically, FIGS.25 and 26 show the difference in behavior between two picture images ofthe interference fringes. FIG. 25A shows the positional relationshipamong the measuring point, the lenses 425, 426, and the CCD camera 424.FIG. 25B shows in a magnified fashion the measuring point. Further, FIG.25C shows the light intensity distribution of a picture image detectedfor measuring the temperature. The letter d in FIG. 25B denotes thedistance between the concave portions P1, P2, and Δd represents theamount of change in the distance d caused by the temperature change. Onthe other hand, FIG. 26A shows the positional relationship between themeasuring point accompanying the temperature change and the CCD camera441. Also, FIG. 26B shows the light intensity distribution of a pictureimage for detecting the moving amount. The symbol ΔD shown in FIG. 26Bdenotes the amount of movement of the light intensity distribution.Further, FIGS. 27A and 27B show the interference fringes B and Sobtained by the CCD cameras 424 and 441, respectively.

[0188] As apparent from FIG. 25C, the interference fringes B and Sdetected by the CCD camera 424 are caused to be incident inpredetermined positions by the lenses 425, 426 even if the wafer ωe isexpanded by the temperature heating so as to move the measuring point.

[0189] On the other hand, FIG. 26B shows that the light intensitydistribution is moved by an amount of ΔD, which is close to the actualmoving amount, in the case of the picture image for detecting the movingamount. FIG. 28 shows the principle for obtaining the moving amount fromthe light intensity distribution. Specifically, for improving theaccuracy, changes in plural maximal values are calculated to obtain anaverage value in analyzing the changes in the positions of the maximalvalues before and after the movement. The true moving amount can beobtained by comparing the data of the moving amount thus obtained withknown data, followed by correcting the resultant error.

[0190] There now follows a description of how to correct the errorcaused by the beam diameter of the laser beam L. Specifically, the laserbeam itself exhibits an intensity distribution, as shown in FIG. 29,with the result that an error is generated if the measuring point ismoved only slightly, even if the laser is stationary. Therefore, theerror is less likely to be affected by the movement of the measuringpoint if the intensity distribution of the laser beam is flat, i.e.,with increase in the beam diameter. The error caused by the slightmovement can be corrected by detecting the moving amount.

[0191] There now follows a description of how to correct the lensaberration of the lenses 425, 426. As described previously, the incidentpoint of the interference fringes S is not changed by the lenses 425,426, making it unnecessary to adjust the position of the CCD camera 424.However, since the interference fringes S pass through the outerperipheral portions of the lenses 425, 426, the picture image of theinterference fringes S is distorted under the influences of the lensaberration. FIG. 30 is a graph showing the relationship between themeasuring error caused by the lens aberration and the moving amount(measuring position). Incidentally, the moving amount zero (0) on theabscissa of the graph denotes the case where the interference fringespass through the center of the lens, i.e., interference fringes B.

[0192] The error is defined to be an error from the frequency in thecentral position of the lens by the result of calculation of thefrequency under the condition of a constant temperature. The particularrelationship remains unchanged unless a lens having differentcharacteristics is substituted. Therefore, the error can be corrected ifthe quantitative characteristics of the particular relationship are usedas a known value.

[0193] As shown in FIG. 30, even a slight moving amount leads to a largeerror under the influence of the lens aberration if the position beforethe movement is on the outer circumferential region of the lens.Therefore, a distortion ε is corrected as follows.

[0194] Specifically, the actually measured frequency and the error atthe position before the movement are set at f1 and Δε1, respectively.Likewise, the actually measured frequency and the error at the positionafter the movement are set at f2 and Δε2, respectively. In this case,the frequency f0 before the movement and the frequency f0′ after themovement are represented by formulas given below:

f 0=f 1×{100/(Δε1+100)}  (1)

f 0′=f 2×{100/(Δε2+100)}  (2)

[0195] Therefore, the distortion ε is represented by:

ε=(f 0′−f 0)/f 0  (3)

[0196] As described above, the temperature measuring apparatus 410according to the ninth embodiment of the present invention makes itpossible to measure the surface temperature of a wafer during the filmforming process highly accurately in a non-contact manner by utilizing aconcave and convex pattern such as an L/S pattern having the highestprobability of presence in each step of a manufacturing process of asemiconductor device. Therefore, a special pattern need not be formed,and the temperature can be measured highly accurately.

[0197] Also, the distance between adjacent fringes of the interferencefringes is calculated by the frequency analysis, making it possible toperform the temperature measurement highly accurately regardless of theresolution of the CCD camera 424. Further, the frequency analysis of thesine wave is performed by using the maximum entropy method, leading to ameasurement of a higher accuracy.

[0198] On the other hand, the lenses 425, 426 are used for allowing theinterference fringes to be incident on the CCD camera 424 at apredetermined position, making it unnecessary to enlarge or move the CCDcamera 424. It should also be noted that the lenses 425, 426 and the CCDcamera 424 are integrally arranged within the optical cylinder 427.Therefore, it is possible to ensure a rigidity, to improve the measuringaccuracy and to prevent intrusion of the disturbing light. Further,since the inner surface of the optical cylinder 427 is coated with alight absorbing material, it is possible to prevent the irregularreflection of light within the optical cylinder 427.

[0199] Further, the aberration of the lenses 425, 426 can be correctedby detecting the moving amount of the interference fringes, leading tothe temperature measurement of a further improved accuracy.

[0200] Further, the irradiating position of the laser beam L can bechanged by using the prism 422 so as to make it possible to measure thetemperature at plural positions of the wafer. It follows that it ispossible to measure the average temperature of the wafer ωe.

[0201] Still further, since the beam diameter adjuster 443 is mounted,it is possible to select the beam diameter adapted for the temperaturemeasurement.

[0202] The present invention is not limited to the embodiment describedabove. For example, in the embodiment described above, a CCD camera isused in the light detecting section. However, it is also possible to usea line sensor or an area sensor prepared by arranging plural linesensors. Of course, the present invention can be worked in variouslymodified fashions within the technical scope of the present invention.

[0203]FIG. 31 shows a CVD apparatus (process apparatus) 510 including afilm thickness measuring apparatus according to a tenth embodiment ofthe present invention.

[0204] The CVD apparatus 510 includes a film forming section 520 and afilm thickness measuring section 530. A semiconductor wafer εf is usedas a substrate in the CVD apparatus 510.

[0205] The film forming section 520 includes a chamber 521 housing thesemiconductor wafer εf, a rotating mechanism 522 for rotating thesemiconductor wafer εf housed in the chamber 521 in a direction denotedby an arrow r in FIG. 31, and a process section 523 in which apredetermined treatment is applied to the semiconductor wafer εf. Asshown in the drawing, a view port 521 a is formed in the upper surfaceof the chamber 521.

[0206] The film thickness measuring section 530 includes a lens 531 forcollecting the light R radiated from the semiconductor wafer εf throughthe view port 521 a, an optical fiber 532 having one end positioned toface the lens 531 for guiding the radiated light R, a spectroscope 533aligned with the other end of the optical fiber 532, a measuring section534 for measuring the intensity of the light split from the radiatedlight R by the spectroscope 533, a memory section 540 connected to themeasuring section 534 and storing various data referred to later, anarithmetic section 550 connected to the measuring section 534 and thememory section 540 for performing arithmetic operations referred tolater, and a control section 560 connected to the arithmetic section 540for controlling the film forming section 520 based on the arithmeticoperations performed in the arithmetic section 550.

[0207] The memory section 540 includes a reference waveform memorysection 541 for storing a waveform ε1 (waveform of light radiated from areference sample) of the light split from the light radiated from thewafer ωf (reference wafer) before formation of the underlying film, afirst memory section 542 storing a first data base representing therelationship between a peak wavelength and the thickness of theunderlying film, said peak wavelength being obtained by dividing awaveform (waveform of light radiated from a measured sample) ω2 of thelight radiated from the wafer ωf (measured wafer) after formation of theunderlying film by the waveform ω1 of the light radiated from thereference sample, and a second memory section 543 storing a second database representing the relationship between a peak wavelength and thethickness of the uppermost film, said peak wavelength being obtained bydividing a waveform ω3 of the process radiation for every thickness ofthe underlying film by the waveform ω2 of the measured sample radiation.It should be noted that the term “data base” noted above represents agraph or formula showing the relationship between the peak wave lengthand the film thickness. Also, “waveform” denotes a graph showing therelationship between the intensity and the wavelength.

[0208] The arithmetic section 550 includes a first arithmetic section551 for calculating the thickness of the underlying film of the wafer ofbefore the film formation thereon on the basis of the measured sampleradiation waveform ω2 obtained in the measuring section 534 and thefirst data base stored in the first memory section 542, and a secondarithmetic section 552 for calculating the peak wavelength obtained bydividing the process radiation waveform ω3 obtained in the measuringsection 534 by the measured sample radiation waveform ω2, saidcalculation being performed on the basis of the data base stored in thesecond memory section 537.

[0209] In the CVD apparatus 510 of the construction described above, thethickness of the uppermost film is measured and the film formation iscontinued until the thickness of the film reaches a predetermined valueas follows. It should be noted that the reference sample radiationwaveform ω1 is stored in advance in the reference waveform memorysection 541. Also, the first data base (see FIG. 32) and the second database (see FIG. 33) are also stored in advance in the first memorysection 542 and the second memory section 543, respectively.

[0210]FIG. 32 is a graph showing the relationship between a peakwavelength and the thickness of an underlying film, covering the casewhere the underlying film of TEOS (tetraethyl ortho-silicate) is formedin a thickness of 4000 to 6000 Å on the semiconductor wafer ωf, saidpeak wavelength being obtained by dividing the split radiation waveformbefore formation of the underlying film. On the other hand, FIG. 33 is agraph showing the relationship between a peak wavelength and thethickness of an underlying film, covering the case where the uppermostpoly-Si film is formed in a thickness of 5000 Å on the semiconductorwafer ωf having the underlying film formed thereon in advance, said peakwavelength being obtained by dividing the process radiation waveform ω3by the measured sample waveform ω2.

[0211]FIG. 34 is a flow chart showing the procedure of actually forminga film. This example covers the case where a poly-Si uppermost film isformed in a thickness of 5000 Å on the underlying film.

[0212] In the first step, a radiation waveform is measured under thecondition that an underlying film alone is formed on the semiconductorwafer ωf so as to obtain a measured sample radiation waveform ω2 (ST1).Then, a reference sample radiation waveform ω1 is read out of thereference waveform memory section 541 to have the measured sampleradiation waveform ω2 divided by the reference sample radiation waveformω2 (ST2) so as to obtain a peak wavelength (ST3).

[0213] Then, the first data base is read out of the first memory section542 so as to calculate the thickness of the underlying filmcorresponding to the peak wavelength (ST4). Further, the second database is read out of the second memory section 543 so as to obtain thepeak wavelength at the time when the poly-Si uppermost film is formed ina thickness of 5000 Å based on the thickness of the underlying filmcalculated in step ST4 (ST5). The peak wavelength thus obtained istransmitted to the control section 560.

[0214] On the other hand, a film is formed on the semiconductor wafer ωfin the film forming section 520, and the process radiation waveform ω3during the film formation is continuously measured in the film thicknessmeasuring section 530 (ST6). The process waveform ω3 thus obtained isdivided by the measured sample radiation waveform ω2 (ST6) so as toobtain a peak wavelength (ST8). When the peak wavelength thus obtainedcoincides with the peak wavelength obtained in step ST5, the operationproceeds to step ST9. When the peak wavelength does not coincide withthe peak wavelength obtained in step ST5, the operation is brought backto step ST6. In step ST9, a command signal to stop the film formation issupplied from the control section 560 to the film forming section 520.

[0215] For example, where the peak wavelength obtained in step ST4 is725 nm, the operator understands that the thickness of the underlyingfilm is 5000 Å. This indicates that it suffices to stop the filmformation at the peak wavelength of 675 nm in step ST5 in the case offorming a poly-Si film in a thickness of 5000 Å.

[0216] Also, where the peak wavelength obtained in step ST4 is 708 nm,the operator understands that the thickness of the underlying film is4500 Å. This indicates that it suffices to stop the film formation atthe peak wavelength of 648 nm in step ST5 in the case of forming apoly-Si film in a thickness of 5000 Å.

[0217] As described above, in the CVD apparatus 510 according to thetenth embodiment of the present invention, the thickness of theuppermost film during the film formation is measured in accordance withthe thickness of the underlying film, making it possible to measureaccurately the film thickness without being affected by the differencein thickness of the underlying film. It follows that formation of theuppermost film can be stopped at a target thickness of the film with ahigh accuracy.

[0218] The present invention is not limited to the tenth embodimentdescribed above. For example, the tenth embodiment is directed to a CVDapparatus as a process apparatus. However, the technical idea of thetenth embodiment can also be applied to an etching apparatus. Also, aradiated light is utilized in the tenth embodiment. However, it is alsopossible to irradiate the wafer with light so as to utilize the lightreflected from the wafer. Needless to say, the present invention can beworked in variously modified fashions within the technical scope of thepresent invention.

[0219] Additional advantages and modifications will readily occur tothose skilled in the art. Therefore, the invention in its broaderaspects is not limited to the specific details and representativeembodiments shown and described herein. Accordingly, variousmodifications may be made without departing from the spirit or scope ofthe general inventive concept as defined by the appended claims andtheir equivalents.

1. A temperature measuring method, comprising the steps of: detecting anintensity of light radiated from an object and an intensity of lightreflected from said object when the object is illuminated with light;determining a reflectivity of the object from the intensity of thereflected light and a reference intensity for the reflected light; anddetermining the temperature of the object from an emissivity obtainedfrom the reflectivity of the object and the intensity of the lightradiated from the object.
 2. A temperature measuring method, comprisingthe steps of: detecting an intensity of light radiated from an object,an intensity of light reflected from the object when the object isilluminated with light, and an intensity of light transmitted throughthe object when the object is illuminated with light; determining areflectivity of the object from the intensity of the reflected light anda reference intensity for the reflected light; determining atransmittance of the object from the intensity of the transmitted lightand a reference intensity for the transmitted light; and determining thetemperature of the object from the reflectivity and from an emissivityobtained from the transmittance of the object and the intensity of thelight radiated from the object.
 3. A temperature measuring apparatus,comprising: first intensity detecting means for detecting an intensityof light radiated from an object; second intensity detecting means fordetecting an intensity of light reflected from the object when theobject is illuminated with light; reflectivity calculating means forcalculating a reflectivity of the object from the intensity of thereflected light detected by said second intensity detecting means, andfrom a reference intensity for the reflected light; and temperaturecalculating means for calculating a temperature of the object from anemissivity obtained from the reflectivity calculated by saidreflectivity calculating means and the intensity of the radiated lightdetected by said first intensity detecting means.
 4. A temperaturemeasuring apparatus, comprising: first intensity detecting means fordetecting an intensity of light radiated from an object; secondintensity detecting means for detecting an intensity of light reflectedfrom the object when the object is illuminated with light; thirdintensity detecting means for detecting an intensity of lighttransmitted through the object when the object is illuminated withlight; reflectivity calculating means for calculating the reflectivityof the object from the intensity of the reflected light detected by thesecond intensity detecting means and a reference intensity for thereflected light; transmittance calculating means for calculating atransmittance of the object from the intensity of the transmitted lightdetected by the third intensity detecting means and a referenceintensity for the transmitted light; and temperature calculating meansfor calculating a temperature of the object from the reflectivitycalculated by the reflectivity calculating means, an emissivity obtainedfrom the transmittance calculated by the transmittance calculatingmeans, and the intensity of the radiated light detected by the firstintensity detecting means.
 5. A temperature measuring apparatus,comprising: a light source, light transmitting means for transmittinglight radiated from said light source to a surface of an object and fortransmitting light reflected from and radiated from the object;switching means designed to apply the light radiated from the lightsource and to stop applying the light radiated from the light source;intensity calculating means for alternately receiving light reflectedfrom, and light radiated from, the object, both being transmitted bysaid light transmitting means in synchronism with the operation of saidswitching means, thereby to calculate an intensity of the reflectedlight and an intensity of the radiated light; reflectivity calculatingmeans for calculating an reflectivity of the object from the intensityof the reflected light calculated by said intensity calculating meansand a reference intensity for the reflected light; and temperaturecalculating means for calculating a temperature of the object from anemissivity determined from the reflectivity obtained by the reflectivitycalculating means and the intensity of the radiated light calculated bysaid light intensity calculating means.
 6. The apparatus according toclaim 5, wherein interference filters capable of transmitting only lightcomponents having predetermined wavelengths are arranged on the opticalpaths of the light radiated from the light source, and the light beamsreflected and radiated from the object.
 7. The apparatus according toclaim 5, wherein a spectroscope is provided which splits only a lightcomponent having a predetermined wavelength, which is selected fromamong the light radiated from the light source and the light beamsradiated and reflected from the object.
 8. The apparatus according toclaim 5, wherein said light source radiates light having a spectrumsubstantially equal to that of the light radiated from the object.
 9. Atemperature measuring apparatus, comprising: a light source; intensitycalculating means for alternately receiving light reflected from, andlight radiated from, the object, both being transmitted by said lighttransmitting means in synchronism with the operation of said switchingmeans, thereby to calculate an intensity of the reflected light and anintensity of the radiated light; transmitted light intensity calculatingmeans for receiving light transmitted through the object in synchronismwith the operation of said switching means, thereby to calculate anintensity of the transmitted light; reflectivity calculating means forcalculating a reflectivity of the object from the intensity of thereflected light calculated by said intensity calculating means and areference intensity for the reflected light; transmittance calculatingmeans for calculating a transmittance of the object from the intensityof transmitted light calculated by said transmitted light intensitycalculating means and a reference intensity for the transmitted light;and temperature calculating means for calculating a temperature of theobject from the emissivity determined from the reflectivity obtained bythe reflectivity calculating means and from the transmittance calculatedby said transmittance calculating means and the intensity of theradiated light calculated by said intensity calculating means.
 10. Theapparatus according to claim 9, wherein interference filters capable oftransmitting only light components having predetermined wavelengths arearranged on optical paths of the light radiated from the light sourceand on optical paths of light beams reflected and radiated from theobject.
 11. The apparatus according to claim 9, wherein a spectroscopeis provided which splits only a light component having a predeterminedwavelength, which is selected from among the light radiated from thelight source and the light beams radiated and reflected from the object.12. The apparatus according to claim 9, wherein said light sourceradiates light having a spectrum substantially equal to that of thelight radiated from the object.
 13. A temperature measuring methodcomprising: a step of splitting light radiated from a substrate intoplural light components having wavelengths ranging over a predeterminedwavelength region; a step of detecting intensity of each of the lightcomponents obtained in said light splitting step; a step of calculatingan integrated value of radiation intensity by cumulatively adding theintensities of said light components, detected in said detecting step;and a step of calculating a surface temperature of said substrate fromsaid integrated value and preset reference data representing a relationbetween the temperature and the integrated value.
 14. A temperaturemeasuring apparatus comprising: a light splitting section for splittinglight radiated from a substrate into plural light components havingwavelength ranging over a predetermined wavelength region; a detectionsection for detecting the intensity of each of the light componentsobtained by said light splitting section; an integrated valuecalculating section for calculating an integrated value of radiationintensity by cumulatively adding the intensities of the lightcomponents, detected by said detecting section; and a surfacetemperature calculating section for calculating a surface temperature ofthe substrate from said integrated value and preset reference daterepresenting a relation between the temperature and the integratedvalue.
 15. A film thickness measuring method for measuring a thicknessof an uppermost film being formed on a substrate, said methodcomprising: a step of actually measuring an intensity distribution oflight radiated from said substrate; a step of calculating a relativeintensity distribution of the radiated light, which is a ratio of theactually measured intensity distribution of the radiated light to areference intensity distribution obtained for the radiated light on thebasis of the light radiated from the substrate before initiation of thefilm formation; and a step of calculating the thickness of the film bycomparing a theoretical intensity distribution of the radiated light,derived from transmitted light theory, with said relative intensitydistribution of the radiated light.
 16. The method according to claim15, wherein said comparison between the theoretical intensitydistribution and the relative intensity distribution is performed bywaveform matching.
 17. The method according to claim 15, wherein saidcomparison between the theoretical intensity distribution and therelative intensity distribution is performed on the basis of a maximumwavelength shift which the relative intensity distribution has withrespect to the theoretical intensity distribution.
 18. A film thicknessmeasuring apparatus for measuring a thickness of an uppermost film beingformed on a substrate, said method comprising: an intensity distributionmeasuring section for actually measuring an intensity distribution ofradiated light on the basis of light radiated from the substrate; arelative intensity distribution calculating section for calculating arelative intensity distribution of radiated light, which is a ratio ofthe actually measured intensity distribution of the radiated light to areference intensity distribution obtained on the basis of light radiatedfrom the substrate before initiation of the film formation; and a filmthickness calculating section for calculating a thickness of the film bycomparing the theoretical intensity distribution of the radiated lightderived from transmitted light theory with the relative intensitydistribution of the radiated light.
 19. A film thickness measuringmethod for measuring a thickness of an uppermost film being formed on asubstrate, said method comprising: a step of measuring a first splitlight intensity distribution on the basis of light radiated from thesubstrate and light reflected from the substrate illuminated with lightwhich has a broadband spectrum distribution before initiation of thefilm formation; a step of measuring a second split light intensitydistribution on the basis of light radiated from the substrate beforeinitiation of the film formation, said substrate having ceased to beilluminated with light; a step of measuring a third split lightintensity distribution on the basis of light radiated from the substrateand light reflected from the substrate during the film formation, saidsubstrate being illuminated with light having a broadband spectrumdistribution; a step of measuring a fourth split light distributionbased on the light radiated from the substrate during the filmformation, said substrate having ceased to be illuminated with light; afirst arithmetic step for obtaining a reference intensity distributionof only the reflected light on the basis of said first split lightintensity distribution and said second split light intensitydistribution; a second arithmetic step for obtaining an actuallymeasured intensity distribution of only the reflected light on the basisof said third split light intensity distribution and said fourth splitlight intensity distribution; a step of calculating a relative intensitydistribution of the reflected light for obtaining a relative intensitydistribution of the reflected light, which is a ratio of the actuallymeasured intensity distribution of the reflected light to said referenceintensity distribution obtained for the reflected light; and a step ofcalculating a thickness of the film by comparing said relative intensitydistribution of the reflected light with a reference intensitydistribution of the reflected light having a known relation with thethickness of the film.
 20. A film thickness measuring apparatus formeasuring a thickness of an uppermost film being formed on a substrate,said apparatus comprising: a section for measuring a first split lightintensity distribution on the basis of light radiated from the substrateand light reflected from the substrate before initiation of the filmformation, said substrate being illuminated with light having abroadband spectrum distribution; a section for measuring a second splitlight intensity distribution on the basis of light radiated from thesubstrate before initiation of the film formation, said substrate havingceased to be illuminated with light; a section for measuring a thirdsplit light intensity distribution on the basis of light radiated fromthe substrate and light reflected from the substrate during the filmformation, said substrate being illuminated with light having abroadband spectrum distribution; and a section for measuring a fourthsplit light intensity distribution on the basis of light radiated fromthe substrate during the film formation, said substrate having ceased tobe illuminated with light; a first arithmetic section for obtaining areference intensity distribution of only the reflected light on thebasis of the first split light intensity distribution and the secondsplit light intensity distribution; a second arithmetic section forobtaining an actually measured intensity distribution of only thereflected light on the basis of the third split light intensitydistribution and the fourth split light intensity distribution; a thirdarithmetic section for obtaining a relative intensity distribution ofthe reflected light, which is a ratio of the actually measured intensitydistribution of the reflected light to the reference intensitydistribution of the reflected light; and a film thickness calculatingsection for calculating a thickness of the film by comparing saidrelative intensity distribution of the reflected light with thereference intensity distribution of the reflected light which has aknown relation with the film thickness.
 21. A wafer temperaturemonitoring apparatus for monitoring a temperature of a wafer having apredetermined pattern formed therein, said apparatus comprising: a laserbeam applying section for illuminating said pattern with laser beam; asensor for receiving diffracted light reflected from the pattern; a lensinterposed between said sensor and the pattern and spaced from thesensor by a distance equal to a focal length of the lens; and anarithmetic section for calculating a temperature of the wafer on thebasis of a position of a spot image formed on said sensor.
 22. A filmthickness monitoring apparatus comprising: a laser beam applying sectionfor illuminating a pattern formed on a wafer, with laser beam; a sensorfor receiving diffracted light reflected from the pattern; and a filmthickness measuring section for measuring a thickness of a thin filmformed on the wafer on the basis of an intensity of the diffracted lightreceived by the sensor.
 23. A wafer temperature-thickness monitoringapparatus for monitoring a temperature of a wafer having a predeterminedpattern formed thereon and a thickness of a film formed on the wafer,said apparatus comprising: a laser beam applying section forilluminating said pattern with laser beam; a sensor for receivingdiffracted light reflected from the pattern; a lens arranged betweensaid sensor and the pattern and spaced from the sensor by a distanceequal to a focal length of the lens; an arithmetic section forcalculating a temperature of the wafer on the basis of a position of aspot image formed on the sensor; and a thickness measuring section formeasuring a thickness of the film formed on the wafer on the basis of anintensity of diffracted light received by the sensor; wherein said wafertemperature and said film thickness are measured simultaneously.
 24. Atemperature measuring apparatus comprising: a laser beam applyingsection for illuminating a pair of reflecting surfaces of an object witha laser beam; a light detecting section for detecting interferencefringes generated by light reflected from said pair of reflectingsurfaces; and an arithmetic section for calculating a temperature on thebasis of a distance between adjacent one of the interference fringesdetected by said light detecting section.
 25. The measuring apparatusaccording to claim 24, wherein a sine wave obtained from an intensityspectrum distribution of the interference fringes obtained in said lightdetecting section is subjected to a frequency analysis in saidarithmetic section, thereby to calculate a distance between the adjacentones of the interference fringes.
 26. The apparatus according to claim25, wherein a maximum entropy method is employed in said arithmeticsection for perform frequency analysis of the sine wave.
 27. Theapparatus according to claim 24, wherein an optical system forcorrecting changes is interposed between said light detecting sectionand the object such that positions of the interference fringes incidenton the light detector remain unchanged even if positions of said pair ofreflecting surfaces are changed.
 28. The apparatus according to claim27, wherein said optical system and said light detecting section areprovided together within an optical cylinder.
 29. The apparatusaccording to claim 28, wherein a inner surface of said optical cylinderis coated with a light absorbing material.
 30. The apparatus accordingto claim 27, wherein an influence of aberration of said optical systemon said interference fringes is corrected on the basis of a distancesaid pair of reflecting surfaces moves.
 31. The apparatus according toclaim 24, further comprising a light detector for measuring a distancesaid interference fringes move, from which a distance said pair ofreflecting surfaces move is calculated.
 32. The apparatus according toclaim 24, wherein an optical system for determining a position of thelaser beam incident on said object is interposed between said laser beamapplying section and said object.
 33. The apparatus according to claim32, wherein said optical system determines positions in at least twodirections on the surface of the object.
 34. The apparatus according toclaim 24, wherein a filter capable of transmitting only light having awavelength of said laser beam is mounted in front of said lightdetector.
 35. The apparatus according to claim 24, wherein a beamdiameter adjuster capable of changing a beam diameter of the laser beamis interposed between said laser oscillator and said object.
 36. Atemperature measuring method comprising: a laser beam applying step forilluminating a pair of reflecting surfaces of an object with a laserbeam; a light detecting step for detecting interference fringesgenerated by light reflected from said pair of reflecting surfaces; andan arithmetic step for calculating a temperature on the basis of adistance between adjacent ones of the interference fringes detected inthe light detecting step.
 37. A film thickness measuring apparatus formeasuring a thickness of an uppermost film formed on a wafer having anunderlying film formed thereon, said apparatus comprising: a measuringsection for measuring intensity of split light radiated from the waferor the intensity of split light reflected from said wafer; a memorysection for storing a data base prepared on the basis of intensity ofsplit light radiated or reflected from a reference sample beforeformation of an underlying film on the wafer, and on the basis ofintensity of split light radiated or reflected from the measured sampleafter formation of the underlying film on the wafer; and an arithmeticsection for calculating a thickness of the uppermost film on the basisof the intensity of the split light radiated or reflected from thesubstrate, during the film formation process, and on the data basestored in said memory section.
 38. The thickness measuring apparatusaccording to claim 37, wherein said data base includes: a first database storing the relationship between a wavelength at a peak position ofa waveform and the thickness of said underlying film, said waveformhaving been obtained by dividing the intensity of the split lightradiated or reflected from the measured sample, by the intensity of thesplit light radiated reflected form the reference sample; and a seconddata base storing a relationship between the wavelength at a peakposition of a waveform and the thickness of the uppermost film, saidwaveform having been obtained by dividing the intensity of the splitlight radiated or reflected during the film formation process, by theintensity of the split light radiated or reflected from the underlyingfilm formed on the measured sample.
 39. A film thickness measuringmethod for measuring a thickness of an uppermost film when a workingprocess is applied to a substrate having an underlying film formedthereon, said method comprising: a step of measuring intensity of asplit light radiated or reflected from a reference sample of saidsubstrate before formation of an underlying film on said substrate; astep of measuring intensity of a split light radiated or reflected froma measured sample of said substrate after formation of an underlyingfilm on the substrate; a step of measuring intensity a split lightradiated or reflected during the film formation process on thesubstrate; a step of calculating a thickness of the underlying film onthe basis of a peak position obtained by dividing the intensity of thesplit light radiated or reflected from said measured sample, by theintensity of the split light radiated or reflected from said referencesample; and a step of calculating a thickness of the uppermost film onthe basis of a peak position obtained by dividing the intensity of thesplit light radiated or reflected during the film formation process, bythe intensity of the split light radiated or reflected from the measuredsample; wherein a relationship between the peak position for everythickness of the underlying film and the thickness of the uppermost filmis calculated in said step of calculating the thickness of the uppermostfilm, said peak position having been stored in advance based on thethickness of the underlying film obtained in said step of calculatingthe thickness of the underlying film.
 40. A process apparatus forapplying a film formation process to a substrate having an underlyingfilm formed thereon, said apparatus comprising: a measuring section formeasuring intensity of a split light radiated or reflected from saidsubstrate; a memory section for storing a data base prepared on thebasis of intensity of a split light radiated or reflected from areference sample of the substrate before formation of an underlying filmand intensity of a split light radiated or reflected from a measuredsample of the substrate after formation of an underlying film; anarithmetic section for calculating a thickness of an uppermost film onthe basis of intensity of split light radiated or reflected during thefilm formation on the substrate and also on the basis of a data basestored in the memory section; and a control section for stopping thefilm formation process when the thickness of the uppermost film reachesa predetermined value.